1. Field of the Invention
The present invention relates to a method for compressing and extracting image data of an OSD image displayed by an OSD (On Screen Display) function of a display.
2. Description of the Related Art
Conventionally, an image data output device that executes an OSD function has been introduced commercially. The OSD function is a function to improve user operability, and specifically, a function to display images showing the operating state, the operating method, and the like of an apparatus main unit to which this image data output device is applied, on a screen of a display device connected to the apparatus main unit.
The image data output device provided with such an OSD function is applied to various apparatus, such as a receiver apparatus for receiving television broadcasts, which is a so-called set-top box, and a DVD player apparatus for reproducing data recorded in DVDs (Digital Versatile Disks). The image data output device applied to the set-top box, for example, allows a display device to display an OSD image that indicates the channel number of the channel currently received by the main unit. Likewise, the image data output device applied to the DVD apparatus allows a display device to display an OSD images that indicates the state of reproducing operations such as pause, fast forward, and rewind.
The image data output device has an OSD memory that stores OSD image data to be displayed on a screen of a display device using the OSD function, reads out and outputs the OSD image data stored in this OSD memory in response to the operating state at the time.
An image-data compressing method of compressing OSD image data for the purpose of reducing the capacity of the OSD memory that stores OSD image data as small as possible has been conventionally known (for example, see JP-A-2003-087790). In this conventional image-data compressing method, the pixel at the top-left corner in image data is set as a start point pixel. Then, the number of pixels being contiguous from the start point pixel along the scanning direction and having the same image data as that of the start point pixel is obtained. Further, the next pixel to the pixels the number of which was obtained here, that is, the first pixel having a different pixel data from that of the start point pixel among the pixels contiguous along the scanning direction from the start point pixel is set as a new start point pixel, and the number of pixels contiguous along the scanning direction and having the same image data as the start point pixel is obtained. This operation is repeated, and thereby it is possible to obtain compressed data including a plurality of data in which the image data of each start point pixel is paired with the number of the pixels having the same pixel data as that of the start point pixel and being contiguous along the scanning direction.